Water heater construction

ABSTRACT

A water heater construction and method includes arranging the inner water tank and the surrounding outer shell in an inverted orientation and positioning the outer shell into a cover which is arranged with clearance openings for the plumbing connections extending from the top of the tank to extend therethrough. With the tank, shell and cover in an inverted and assembled condition, the annular clearance space defined between the tank and shell is filled, at least the majority, with liquid, foam-in-place insulation. By inverting the water heater and injecting liquid foam insulation material, the clearance space above the inner water tank is foamed first thereby assuring that the foam material at this location will have greater uniformity in foam density and cell structure than at the lower portion of the annular space so as to provide enhanced thermal efficiency at the most critical location.

This application is a division of application Ser. No. 392,342, filed8/11/89 now U.S. Pat. No. 4,992,223.

BACKGROUND OF THE INVENTION

Conventional water heater construction includes a generally cylindricalouter shell concentrically placed around the inner water tank leaving anannular space therebetween. The construction is completed by fillingthis annular space with some type of thermal insulation material,typically liquid, foam-in-place insulation material. The construction iscompleted by putting some type of top cover or enclosure over the top ofthe inner water tank and over the upper top edge of the outer shell soas to enclose the annular space. Likewise, some type of lower or basecover or enclosure is provided beneath the water tank in a similarfashion.

The specific arrangement of foam insulation within the annular space mayinclude any of the variations disclosed by the following U.S. Pat. Nos.:

    ______________________________________                                        U.S. Pat. No.   Patentee Issue Date                                           ______________________________________                                        4,477,399       Tilton   10/16/1984                                           4,527,543       Denton   07/09/1985                                           4,736,509       Nelson   04/12/1988                                           4,744,488       Nelson   05/17/1988                                           4,749,532       Pfeffer  06/07/1988                                           ______________________________________                                    

Tilton discloses a method for insulating a water heater with foamedinsulation and includes inflating a tube in the cavity between the shellof the tank in order to define a boundary for the cavity into which theinsulating material is injected. The device is then deflated after thefoamed insulation has set in the cavity.

Denton discloses a water heater construction with an insulating spacebetween the outer cover member and the inner water tank. A cover is usedon the top in order to close off the insulating space and an insulatingwall is provided in the insulating space between the tank and the outercover. The insulating wall is comprised of a plastic envelope member anda wall of insulating material which has been foamed-in-place inside theplastic envelope member.

Nelson U.S. Pat. No. '509 discloses a method of making a water heaterwhich includes the steps of locating a sleeve of insulation materialaround the exterior wall surface of the inner tank extending fromapproximate the bottom end of the inner tank and extending upwardlylongitudinally thereof a predetermined distance which is less than thefull length of the inner tank. The next step is folding the top end ofthe insulation sleeve back over itself in order to form an annular cuffat the top end of the sleeve and the positioning the outer shellconcentrically over the inner tank whereupon the annular cuff iscompressed between the interior wall surface of the outer shell and theexterior wall surface of the inner tank. The annular clearance spaceabove the annular cuff of the sleeve is then filled with an expandablefoam insulation material which is allowed to foam in place.

Nelson U.S. Pat. No. '488 discloses a water heater construction where acontrol apparatus, such as a thermostat, is located on the exterior wallsurface of the inner tank and the outer shell includes an aperture whichis in alignment with the control apparatus. The specific inventioninvolves the disclosure of a collar which is located around the controlapparatus and is compressed between the inner tank and the outer shellin order to provide a sufficiently sealed barrier around the thermostatsuch that when the space between the inner tank and the outer shell isfilled with a foam insulation material, this foam insulation materialwill not interfere with the thermostat or other control which may besealed around by this invention.

The Pfeffer patent discloses a water heater construction wherein foaminsulation fills a cavity between the tank and the outer shell and isdisposed above a bottom wall which is formed by a preassembledfiberglass belt. This fiberglass belt is wrapped and secured around theouter diameter of the tank by an encircling and compressing band. Thetop and bottom edges of the belt flare outwardly to a diameter sizewhich is in excess of the inner diameter of the shell. A flat, flexibleplastic sheet is used much like a shoehorn in order to compress the beltas the outer shell is lowered into position. This flexible plastic sheetis then removed and the space above the belt is foamed withfoam-in-place insulation material.

The specific configuration of the foam insulation depends in part onwhether the particular water heater is gas or electric. Whenconstructing an electric water heater, the lower portion of the tankdoes not have special insulation requirements. However, there areoperational controls which must be insulated around and a suitabletechnique for such insulating is disclosed in U.S. Pat. No. 4,744,488which is expressly incorporated herein by reference.

When constructing a gas water heater, the lower portion of the tankrepresents a particularly hot area with special insulating requirements.Liquid foam insulation is not suitable for this hot area and fiberglassmatting or batt material is used instead. A further feature of typicalwater heater construction is the need for the water inlet and outletfittings (pipes) to exit from the tank through the top cover portion ofthe outer enclosure which is either attached to or fabricated as part ofthe outer generally cylindrical shell. When a gas water heater isconstructed, a flue for the byproducts of the combustion must beprovided out the top of the shell in addition to the inlet and outletwater conduits. These conduits and the exhaust flue must be sealedaround at the interface with the enclosure or top cover so that as theliquid, foam-in-place insulation rises and expands, it does not leak outaround the conduits and flue. In the typical construction approach, atop cover and a bottom cover are assembled to the shell in order to forman enclosed, exterior cylinder.

A variety of insulation materials and insulating methods are used intypical water heater construction in an attempt to produce anenergy-efficient unit at the lowest possible cost based on materials andmanufacturing labor. This desire has led to the development of manymethods for insulating water heaters with a liquid, foam-in-placeinsulation material such as urethane or polyisocyanurate insulationmaterial. All of the methods currently being used entail the use ofsealing devices of some type in order to keep the foam insulation withinthe space between the tank and the outer cylindrical shell. Thisapproach can be costly in terms of material and labor and othermanufacturing concessions may need to be made, such as assembly linespeed, in order to accommodate the placement of the sealing deviceswithin the cavity formed by the tank and shell.

Gas-fired water heaters and electric powered water heaters havedifferent design features and thus the sealing considerations prior tofoaming are different for each. However, in most conventionalmanufacturing methods, there are similar constraints for effectivelysealing the cavity between the tank and shell. In all commonly usedmethods, there are several drawbacks that greatly increase the cost ofachieving a given energy rating for the water heater. These methods arealso a less-efficient use of the costly foam insulation.

The present invention addresses basic principles of the thermodynamicsand the processing characteristics of foam insulation in order toprovide a more efficient water heater. The present governmentalstandards requiring higher-efficiency water heaters makes this inventionparticularly important. Further, the use of fluorocarbons as the mostefficient blowing agent in the foaming process allows foam insulationsto achieve R values in excess of other commonly used insulationmaterials. However, new governmental standards aimed at protecting theenvironment, in particular the earth's ozone layer, are mandatingsharper cuts in the use of fluorocarbons. Although it seen that thedesire to achieve higher efficiency ratings in terms of R value is inconflict with the government's desire to protect the ozone layer, thesecompeting concerns make the present invention even more importantbecause less foam insulation is required to achieve the same insulationR values and thus as a net result, less fluorocarbons are required inthe manufacturing process.

The present invention is directed to the construction of a water heaterwhich is manufactured by first positioning individual sealing gasketsover each protrusion such as plumbing fittings, which extend from thetank, or by first positioning a unitary sealing device over thecollective protrusions and then fitting the tank with a top cover whichis one portion of the enclosing means for the tank. This top cover hasopenings to allow the tank protrusions to extend therethrough. This topcover is further configured in such a way as to contact each individualsealing gasket or the unitary sealing device in order to provide aliquid-tight seal at the interface between the operating connectionsextending from the tank through the top cover with the top cover.

In one approach the next step is to turn or invert the tank and coverassembly so that it is upside down from its normal position so that thetop cover is in the lowermost position and the bottom of the tank hasassumed the normal top position. The surrounding generally cylindricalouter shell is then positioned over the tank with a concentric spaceleft between the outer surface of the inner tank and the inner surfaceof the outer shell. Some type of sealing is provided between the shelland the top cover either in individual form or as part of the unitaryseal used around the tank protrusions.

As an alternative approach to these first steps, the cover and thegenerally cylindrical outer shell are preassembled and sealed togetherin order to create a single unit. This assembled single unit of coverand outer shell is placed over the tank prior to inverting the tank.When the inverting step is performed it is performed for both the tankand the cover/shell assembly.

A further alternative is to fabricate the cover and the outer shell asan integral, one-piece member, such as a molded plastic unit and thenassemble this unit over the tank prior to inverting the tank. Thiseliminates the step of sealing together the cover and shell.

In each of the approaches and alternative forms, expandable insulationfoam (liquid, foam-in-place insulation) is injected into the clearancespace between the tank and the top cover and between the tank and thesurrounding outer shell. As this liquid foam expands to fill the space,it rises in effect from the top of the tank toward the bottom of thetank. Since the bottom at this point is open, any space or voids leftthat are not fully foamed are filled with dry insulation such asfiberglass matting or batts which can be easily stuffed into any spaceleft at what will ultimately be the bottom of the foam insulation.Finally, an insulation disc or bottom cover can be placed over thebottom of the tank in order to complete the assembly. After the foam hascured to a sufficient degree, the entire assembly is then inverted backto its normal upright position and the construction is completed.

The value of the present invention evolves from some of the physical andchemical reaction properties of the liquid, foam-in-place insulation.When this insulation material is injected to the annular clearance spacebetween the outer shell and the water tank, when these are in theirnormal upright orientation, the foaming process begins at a lowerportion of the tank along the side of the tank. As the foam rises towardthe top of this annular clearance space, the quality of the foamdecreases. The lowermost portion of the cavity which is foamed firstwill have a higher-density foam, and a more uniform density and amore-consistent cell structure to the foam than the uppermost portion ofthe cavity. This particular result is contrary to the generalthermodynamic theory and the heat transfer realities as to heat lossesfrom the inner water tank. Heat transfer and thermodynamics tell us thatit is preferred to have the top of the unit better insulated than thelower side portion in order to achieve the most energy-efficient designbased upon using a fixed or given volume of foam.

To further compound the manufacturing problems of current foamingmethods, a predetermined amount of liquid is injected into the annularspace between the shell and the tank and the manufacturing methods relyon the accuracy and consistency of the foam machinery in order to injectexactly the same amount of foam with each unit being constructed.However, there are variations in the cavity volume and variations in howaccurately the amount of liquid foam can be controlled as well as simplyvariations in the foaming process due to the chemistry of the insulationmaterial. The result, as is believed to be well known, is noticeablevariations from one water heater to another thus meaning that there isno guarantee that for any one water heater, the annular clearance spaceincluding the space between the outer enclosure and the top of the watertank is completely filled with foam insulation. It is known that whenunder-foamed, the most critical top portion of the tank has insulationvoids or openings resulting in a very inefficient design. If too muchliquid is injected or if the foam chemistry or temperature vary in sucha way to allow a greater degree of foaming than what has been calculatedfor the available space, the foam leaks out around the plumbing fittingsand other protrusions at the top of the cover and this results in asignificant cleanup and appearance problem.

The necessity of high-speed assembly line production simply cannotadequately deal with these variables, and since the over-fill problemcannot be overlooked due to the unsightly appearance, the tendency is tounder-design the amount of liquid foam so that any over fill iseliminated. The problem as referenced above is that the top portion ofthe clearance space, that portion above the water tank top, is veryinefficiently insulated and thus the thermal insulation efficiency ofthe overall construction is inferior.

As mentioned, the present invention solves this problem by providing amore cost-effective and more energy-efficient unit by guaranteeing thatthe top of the unit will always be insulated fully by foam and that thisportion of the foam will be of a higher quality. With regard to theamount of liquid foam which is used, there is much greater latitude inview of the fact that any under-fill which leaves a small portion of theannular clearance space uninsulated can be filled with dry insulationmaterial such as fiberglass batting. Since in the present invention theentire outer shell and tank is inverted, the portion that does notreceive any foam insulation and is filled with dry insulation materialultimately becomes the bottom or lower portion of the water and is muchless critical from a thermal insulation standpoint.

SUMMARY OF THE INVENTION

A water heater construction according one typical embodiment of thepresent invention includes an inner water tank, an outer enclosuredisposed over and around the inner water tank and defining therebetweena clearance space, thermal insulation material foamed in place betweenthe tank and shell in the clearance space wherein the foamed insulationmaterial has greater uniformity in cell structure and density and agreater or higher density in the upper portion of the volume of foamwhich is disposed over the top of the inner water tank than in the lowerportion of the volume of foam insulation material disposed around theside of the inner water tank.

A method of insulating the clearance space between an inner water tankand an outer enclosure which surrounds and covers the water tankaccording to one embodiment of the present invention comprises the stepsof first inverting the inner water tank and the outer enclosure suchthat the normal position of the top portion of the clearance spacebecomes the lowest portion of the inverted clearance space and theninjecting liquid, foam-in-place insulation material into the clearancespace so as to foam the normal-position top portion first.

One object of the present invention is to provide an improved waterheater construction.

Another object of the present invention is to provide an improved methodfor insulating the annular clearance space between an inner water tankand an outer enclosure.

Related objects and advantages of the present invention will beapparently from the following description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B are diagrammatic illustrations of a prior art foamingmethod for a gas water heater.

FIGS. 2A and 2B are diagrammatic illustrations of a prior art foamingmethod for a gas water heater.

FIGS. 3A and 3B are diagrammatic illustrations of a prior art foamingmethod for an electric water heater.

FIGS. 4A and 4B are diagrammatic illustrations of a prior art foamingmethod for an electric water heater.

FIG. 5 is a diagrammatic, front elevational view in full section of anelectric water heater construction and method according to a typicalembodiment of the present invention.

FIG. 6 is a diagrammatic, front elevational view in full section of thecompleted FIG. 5 water heater construction according to a method of thepresent invention.

FIG. 7 is a diagrammatic, partial front elevational view in full sectionof a gas water heater construction and method according to a typicalembodiment of the present invention.

FIG. 8 is a diagrammatic, partial front elevational view of a unitarytop seal as assembled to an electric water heater according to thepresent invention.

FIG. 9 is an enlarged detail, partial diagrammatic illustration of asealing arrangement for use around a plumbing fitting of the inner watertank according to the present invention.

FIG. 10 is an enlarged detail, partial diagrammatic illustration of analternate sealing arrangement for use around the plumbing fitting of theinner water tank according to the present invention.

FIG. 11 is an enlarged detail, diagrammatic illustration of a sealingarrangement for use around the flue of a gas water heater according tothe present invention.

FIG. 12 is an enlarged detail, diagrammatic illustration of a sealingarrangement for use around the flue of a gas water heater according tothe present invention.

FIGS. 13, 13A, 13B and 13C are diagrammatic, front elevational views infull section of various fixture arrangements for use with the waterheater construction method of the present invention.

FIG. 14 is a diagrammatic, front elevational view of a fixturearrangement for use with the water heater construction method of thepresent invention.

FIG. 15 is a diagrammatic, front elevational view in full section ofplastic plugs installed in the plumbing fittings of the inner water tankaccording to the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

For the purposes of promoting an understanding of the principles of theinvention, reference will now be made to the embodiment illustrated inthe drawings and specific language will be used to describe the same. Itwill nevertheless be understood that no limitation of the scope of theinvention is thereby intended, such alterations and furthermodifications in the illustrated device, and such further applicationsof the principles of the invention as illustrated therein beingcontemplated as would normally occur to one skilled in the art to whichthe invention relates.

The present invention involves a method for foaming gas and electricwater heaters with a liquid, foam-in-place insulation material thateliminates the formation of noninsulated voids in the top of the waterheater. The present invention also is directed to the water heaterconstruction which results from the method for foaming. The presentinvention insures that in virtually every instance the top of the innerwater tank will have high-efficiency foam insulation of uniform densityand uniform cell structure. This is achieved according to the presentinvention by inverting the tank and outer enclosure so that the topportion of the inner tank is the area which is foamed first assuringthat the most uniform and efficient thermal insulation will be in thislocation. The quality of the foam insulation is diminished as the foamrises and since the lower portions of the inner cavity or clearancespace around the water tank receive a lesser quality of foam insulation,this design approach represents the most efficient use of a fixed amountof foam from the standpoint of thermal insulating efficiency. Any voidsleft that the liquid foam does not fill can then be filled with dryinsulation material such as fiberglass and these voids can be readilyidentified and recognized because the tank and shell are inverted.

In order to appreciate the differences between the method andconstruction of the present invention from earlier and current designs,reference is made to the first eight illustrations which are FIGS. 1A-4Bdetailing conventional methods of foaming the annular space between theinner water tank and the outer shell. FIGS. 1 and 2 represent designsfor gas water heaters and FIGS. 3 and 4 represent designs for electricwater heaters. The A portion of each illustration pair discloses theconfiguration of the unit as foaming begins and the B portion of eachillustration pair discloses the final construction appearance.

With reference now to the individual illustrations, FIGS. 1A and 1Brepresent a foaming method for a gas water heater 20 which includes afiberglass batt 21 disposed around the lower portion of tank 22 and onthe inside of outer shell 23. Clearance space 24 which is defined by theinner surface of the outer shell and the outer surface of the inner tankextends up the sides of the inner tank. The top of the outer shell andthe top portion of the tank are both open to the atmosphere whichcommunicates with top open space 25. Included as part of this waterheater construction are water inlet fitting 28, water outlet fitting 29,flue 30 and bottom cover 31.

Represented in part by liquid foam nozzle 32, it is to be understoodthat the clearance space 24 and the top open space 25 are to be filledwith foam-in-place thermal insulation. In order to seal the lowerportion of the annular clearance space 24 from the fiberglass batt 21and from the lower portion of the gas burner, a collar 33 or similarbarrier seal is provided so as to isolate and seal off the lower portionof the clearance space where the fiberglass batt is positioned from theremainder of the space. This design restricts the liquid foam to thatportion of the clearance space above the sealing collar 33. As theliquid foam is injected into the annular clearance space surrounding thewater tank and the top space above the top of the water heater, the foamcell structure and the foam density is at its most uniform compositionwith the initial foaming directly above the annular collar 33. This isalso the location where the foam density is the greatest. As the liquidfoams in place and the foam insulation rises to the top of the topclearance space, the thermal insulating properties of the foam diminishthereby providing less efficient thermal insulation. The last portion tofoam has a less uniform cell structure, less density and less uniformfoam density than the first portion to foam.

As mentioned in the background discussion regarding the presentinvention, the liquid foam is often injected as a pretimed andpremeasured amount and thus as the chemistry of the foam, temperature,humidity and related environmental changes as well as volume changestake place, there will either be too much foam injected which causes anoverfill and a cleanup problem, or there is less liquid injected andcomplete foaming is not achieved such that the level of the foamedinsulation does not cover the top of the inner tank.

Referring to FIG. 1B, the completed gas water heater construction isillustrated in a rarely achieved, idealized form showing that theannular clearance space 24 and the top space 25 have received foamedinsulation and the top of the water heater has been closed with topcover 36.

Referring to FIGS. 2A and 2B, a slightly different prior art version ofa gas water heater construction is illustrated. Gas water heater 37 isillustrated in FIG. 2A as the liquid foam is injected, and in FIG. 2Bafter the liquid foam has foamed in place and the water heater iscompleted including the addition of top cover 38. It is to be understoodthat all aspects of the water heater construction of FIGS. 1A and 1B arethe same as in FIGS. 2A and 2B with one exception. This one exception isthat the annular sealing collar 33 has been removed and the barrier toprevent the liquid foam from seeping in and around the lower wrap offiberglass batting is achieved by the use of impermeable materialenvelope 39. As intended to be illustrated, this envelope which may beconstructed of a flexible plastic material, is draped over the topportion of the water tank with openings which are sealed around for thepassage therethrough of the water inlet and outlet pipes and the flue.The free ends of envelope 39 extend up and over the outer edges of theshell and extend down into the annular clearance space to a point ofnear abutment with the top portion of the fiberglass batting. As liquidfoam is injected into this envelope, it is the envelope which providesan appropriate barrier so that the liquid foam will not seep down intoand around the gas burner portion of the water heater.

In the FIG. 2B illustration, the plastic envelope has been completelyfilled with the liquid foam and top cover 38 has been added so as to capoff or seal closed the top open portion of the water heater.

Referring to FIGS. 3A and 3B, a further prior art version of a method toinsulate the space between a water tank and the outer shell for anelectric water heater is illustrated. Electric water heater 40 includesan inner water tank 41, an outer, generally cylindrical shell 42, alower or base cover 43, a lower seal 44, and a control seal 45. Thegenerally cylindrical nature of tank 41 and the generally concentricnature of outer shell 42 create and define an annular clearance space 48therebetween. The lower seal 44 is used to seal the base cover and loweredge of the outer shell from the seepage or leakage of liquid foam whichis injected into the annular clearance space 48 as illustrated by theliquid foam nozzle. Water inlets and outlets are also provided and aswould be expected. The configuration and design of electric water heater40 is very similar to its gas counterpart as illustrated in FIGS. 1A and1B and again as in FIGS. 2A and 2B.

I FIG. 3B, the completed water heater assembly is illustrated showingthe entire annular clearance space as well as the open space above thewater heater being filled with foamed insulation. A top cover 49 hasbeen added in order to complete the assembly. One difference between agas water heater and an electric water heater involves the components ofthe water heater which must be insulated or sealed from the liquid foam.With the gas water heater, the sensitive areas are around the gas burnerportion at the lower region of the assembly. Consequently, this is thearea isolated from the liquid foam. Another aspect of the gas waterheater is the high temperatures generated around the burner and thus itis important to have fiberglass insulation as provided by fiberglassbatting 21 in lieu of foam due to the ability of the fiberglass towithstand high temperatures.

With the electric water heater construction as illustrated in FIGS. 3Aand 3B, there is not the same concern with regard to the lower portionof the water heater but rather it is important to have some means toinsulate around the controls which extend from the side wall of the tankthrough the outer shell. The sealing around these controls is providedby means of control seal 45 which has the appearance of a generallyrectangular frame and a thickness slightly greater than the radialdistance of separation between the outer surface of the water tank andthe inner surface of the shell. This allows this control seal to beslightly compressed thereby providing a sufficiently tight barrieragainst the intrusion or seepage of liquid foam as the foaming actionoccurs.

Referring to FIGS. 4A and 4B, another version of an electric waterheater 50 is illustrated. In the FIG. 4A illustration, the clearancespace between the tank and the shell is being injected with liquid foamthermal insulation. In the FIG. 4B illustration the foaming has beencompleted and a top cover 51 has been added in order to complete theassembly. The difference between the electric water heater of FIGS. 3Aand 3B and that of FIGS. 4A and 4B is that the lower seal 44 has beenreplaced by fluid impermeable envelope 52. The use of this plasticenvelope as illustrated in FIGS. 4A and 4B is virtually identical to theconfiguration and use of envelope 39 in FIGS. 2A and 2B. The envelopeprovides a means to retain the liquid foam so as to seal that foam fromthe remainder of the assembly. Consequently, there is no need for theadditional lower seal 44 as a means to prevent foam leakage or seepagearound the base portion of the water heater. The envelope provides aneffective seal and this envelope is draped over the top of the tank andextends down the side walls of the tank to the bottom portion adjacentthe lower cover at which point it makes a U-turn and extends up theinner surface of the outer shell and then is draped outwardly over thetop edge of the outer shell, as illustrated.

In each of the completed assembly illustrations of FIGS. 1B, 2B, 3B and4B, the same foam qualities and insulating inefficiencies of the liquidfoam are the same. As believed adequately explained in the backgrounddiscussion regarding the present invention, the liquid foam begins itsfoaming action in the lowermost portion of the annular space or cavitybeing filled and it is at this lower portion that the uniformity of cellstructure and density are the greatest. This is also the area where thefoam composition has the greatest thermal efficiency and greatestthermal insulating values. As the foam rises toward the top of the outershell the insulating qualities of the foam diminish providing lessthermal insulation and less foam uniformity. The additional problem asalready mentioned is that construction is often done on a productionline basis and the amount of liquid foam is measured in advance andcannot compensate for volumetric changes of the clearance space nor canit be adjusted with requisite accuracy for variations in chemicalcomposition and temperature. These various foam deficiencies areaddressed and solved by the present invention.

With reference to FIG. 5, the basic construction concept of the presentinvention is illustrated. In the FIG. 5 illustration, a water heaterconstruction prior to being completely foamed is illustrated. Waterheater 55 in the FIG. 5 illustration is configured as an electric waterheater consisting of an inner water tank 56, a generally cylindrical andconcentrically arranged outer shell 57, a top cover 58 disposed over thetop edge of the outer shell and over the top of the inner water tank andhaving a pair of openings 59 and 60 therein for the exit of the plumbingfittings 61 and 62 for water in and water out, respectively. Thelocation of openings 59 and 60 relative to the outer lip of top cover 58help to guarantee the concentricity of the shell and tank.

As should be clear, the foregoing descriptions with regard to the topand bottom portions of the water heater and its component parts are 180degrees out of phase with what is actually illustrated in FIG. 5. Thereason is that the water heater illustrated in FIG. 5 has been invertedso that its normal upright orientation is reversed and it is in effectresting in an upside down manner on its top portion rather than on itsbase. Consequently, its base area becomes the top or uppermost portionand this is the area open to the atmosphere.

The relative size and shape of the inner water tank 56 and the outershell 57 define an annular clearance space 65 between the outer surfaceof the inner water tank and the inner surface of the outer shell. Theaddition of top cover 58 in combination with the outer shell furtherdefines a top clearance space 66. As is illustrated by liquid foamnozzle 67, the annular clearance space is injected with liquid foam andthis liquid foam initially fills the lower portion of the invertedassembly so as to initially fill top clearance space 66. In order toprevent leakage of the liquid foam through the top cover 58 at the pointof exit of the inlet and outlet water fittings 61 and 62, generallycylindrical gasket seals 68 and 69 are provided around the fittings andtightly against top cover 58.

As the liquid foam continues to be injected into the annular clearancespace as is illustrated, the foaming action occurs with the most uniformfoam as to density and cell structure being positioned over the topportion of the water tank in top clearance space 66 and around the sidesof the water tank closest to its top. Again, references herein to top orbottom refer to the final position of the water heater in its acutal-useorientation, not its orientation for the purposes of the assembly andmethod of fabrication.

Due to the fact that the bottom of the inner water tank is exposed tothe atmosphere as is the bottom edge of the outer shell and the bottomportion of the annular clearance space, it is very easy to watch thefoaming action as it occurs to ensure a complete fill. However, thisparticular foaming method is equally suitable to an automated processwhere the volume of liquid foam to be injected is precisely controlled.As has been mentioned before, variations in volume, temperature,chemical composition, etc. may affect the foam volume based upon a fixedvolume of liquid. Since the greatest expense to the assembly comes fromoverfoaming as opposed to underfoaming, it is anticipated that in anyproduction line arrangement, the amount of liquid will be undersized sothat even a worst case set of variables, the annular clearance spacewill not be overfoamed. Since the lowermost portion surrounding theinner water tank is of very little importance as to the overall thermalinsulating design, it is not particularly critical if a small portion ofthe annular clearance space including the space beneath the water tankis not completely filled with liquid foam insulation. Any voids whichare left in this lower portion can be easily filled with a dryinsulation material such as fiberglass.

The completed electric water heater assembly 55 is illustrated in FIG. 6where the top clearance space 66 and the annular clearance space 65except for a small portion at the base and the portion beneath the innertank is completely filled with foamed insulation. The lowermost portionof the annular clearance space and the space beneath the inner watertank has been filled with fiberglass or molded foam insulation. Themolded foam insulation may be precast or simply the result of a separateliquid foaming step. As mentioned, the reference to beneath applies tothe final end-use orientation of the water heater and not its invertedprocessing orientation. A bottom cover 72 has been added in order tocomplete the assembly. Further, while still illustrated in an invertedorientation so as to correspond with the illustration in FIG. 5, itshould be understood that the FIG. 6 illustration is completed and wouldthen be inverted back to its normal orientation for shipment and use.

Depending upon the particular size and shape of the inner water tankrelative to the outer shell and the bottom cover 72, the fiberglassinsulation which is packed into the lower portion of the annularclearance space beneath the foamed insulation can be configured as acombination of an annular ring 73 extending around the side wall of theinner tank and a planoconvex disc 74 positioned below the inner watertank. It is also possible to configure this fiberglass insulation as asingle member contoured to fit the cavity as illustrated. Acceptablealternatives include placing a premolded piece of foam or injecting orpouring a liquid foaming insulation material into this cavity prior toplacing the bottom cover 72 on the unit.

Referring to FIG. 7, the upper portion of a gas water heater 77 isillustrated in an inverted orientation. Water heater 77 includes theinner water tank 78, the generally cylindrical outer shell 79, top cover80, annular clearance space 81, top clearance space 82 and a series ofgenerally cylindrical gasket seals 83, 84 and 85 which are disposedaround the water inlet, flue and water outlet.

It is to be understood that water heater 77 is virtually identical withelectric water heater 55 as to all construction and physicalcharacteristics for the purposes of the present invention. The primarydifference is that with the gas water heater, there is an exiting flue86 which must be additionally sealed around so that as the liquid foaminsulation is injected into the top clearance space and the upperportion of the annular clearance space, this liquid foam as it foams inplace will not leak around the water inlet and outlet fittings nor willit leak around the exiting flue. The design of the water heater in FIG.7 possesses the same properties of the FIG. 6 construction in that theuniformity of the foam insulation as to density and cell structure isthe most efficient in the top portion of the assembly where the liquidfoam foams in place first.

As occurred with regard to the bottom portion of the annular clearancespace in the construction of water heater 55, the lower portion of waterheater 77 will also include a surrounding collar of fiberglassinsulation. Since the lower portion of the water tank in a gas waterheater is an area where much greater temperatures are generated, theliquid foam for a gas water heater construction will typically not befoamed to the same level. Rather the foaming will stop somewhat short ofa full depth allowing the area adjacent the gas burner to be insulatedwith fiberglass insulation which is more resistant to the highertemperatures.

Referring to FIG. 8, there is illustrated an alternative design for thetop cover of an electric water heater. In the illustration of FIG. 8,water heater 90 includes an inner water tank 91 surrounded by an outergenerally cylindrical shell 92. The top cover 93 is, for example, amolded, rigid plastic cylindrical member with a pair of contoured andflared generally cylindrical protrusions 94 and 95 which are sized andshaped so as to provide a tight interference fit around the entirecircumference of water inlet and water outlet plumbing fittings 96 and97, respectively. This cover and outer shell may be fabricated as anintegral unitary member. With either approach, the thought involved withregard to this modified design for top cover 93 is that this cover canbe forced down over the plumbing fittings and in view of theinterference fit provided further sealing such as the generallycylindrical gasket seals used in earlier embodiments can be eliminated.

While member 93 has been described as a top cover and may be a separatepart or molded integrally with the shell, another variation for member93 is also contemplated by the present invention. While the FIG. 8illustration does not change the concept does. Cover 93 can be regardedas seal 93 which is assembled in the manner illustrated and describedprior to the assembly of the actual top cover (not illustrated in thisalternative). The non-illustrated cover has a size, shape andconfiguration virtually the same as the seal 93, though slightly largerto fit snugly over the seal. This alternative approach enables the useof a wider range of materials for the seal because it does not have tobe or provide a hard-shell top. Sealing around fittings 96 and 97 iseasier with a more pliable or flexible material and while such materialis not always durable enough as a final cover the separate coverprovides the desired hard surface for the top of the water heater.

Referring to FIG. 9, there is an enlarged detail of one plumbing fitting96 as it is assembled to top cover 93 and flared portion 94. As isillustrated in FIG. 9, fitting 96 is internally threaded and flaredportion 94 abuts tightly up against the outer surface of the fitting.

As is intended to be illustrated, the outer surface of fitting 96 andthe inner surface of flared portion 94 have an interference fit in thearea designated as 100 which extends for a few millimeters in lengthcompletely around the circumference of the fitting so as to provide asufficiently tight interface so that the liquid foam will not leak pastthis point. It is also possible to mold the entire cover or seal 93including the flared portions 94 and 95 without any opening but ratherwith a thin membrane 101 which is approximately sized to the outsidediameter size of fitting 96 and which must ultimately be punctured orcut in order to access the interior of the water inlet and water outletfittings. The cutting lines for membrane 101 are illustrated by brokenlines 102. One advantage of this particular design is that the interfacesurrounding fitting 96 is completely sealed regardless of the degree ofinterference fit along the outer diameter surface such that the liquidfoaming can occur without any particular attention to the integrity ofthe seal between the plumbing fittings which must extend through the topcover and the top cover. Once the liquid foam has completely set up theweb or membrane 101 can be cut and removed thereby providing access tothe interior threaded surface of the fittings. It is also believed thatthe weight of the tank and shell in the inverted orientation resting onthe membranes 101 of the cover 93 possess sufficient weight in order toestablish a tight seal at that point so that the interior space of thefittings 96 and 97 will not fill with the liquid foam.

Referring to FIG. 10, a slightly different version of the FIG. 9construction is illustrated. It is to be understood that the waterheater construction of FIG. 10 is virtually identical to that of FIG. 9except that in the FIG. 10 arrangement, a generally cylindrical gasketseal 104 is disposed between the top edge surface of the fitting 105 andthe inside surface of web 106. While top cover 107 and flared portion108 have the same general fit and geometric relationship as was presentwith the construction of FIG. 9, if there is any concern that the weightof the inverted tank resting against the membrane 106 will not besufficient to form a tight enough seal so as to prevent any liquid foamfrom leaking into the interior threaded area of the fitting 105, thenthe presence of gasket seal 104 assures that a tight seal will exist atthat interface and prevent any liquid foam from leaking into theinterior of fitting 105.

Referring to FIGS. 11 and 12, the slightly different construction isillustrated in more of a diagrammatic fashion since the illustrationsare only partial and include only a single generally cylindrical fittingexiting from the top surface of the tank. The construction conceptillustrated by FIGS. 11 and 12 is that the top portion of the inner tank110 may be covered with a foam block 111 which is molded to precise sizeand contour so as to match the top portion of the tank. The invertedinner water tank can then be set down over the foam block 111 so thatfitting 112 extends through the molded opening in the block which issealed against the exiting fitting 112 by generally cylindrical gasketseal 113. This type of foam block 111 also serves to provide a type offixturing and alignment for the tank and shell. Assuming that dimensionsare known and tolerances are controlled, the outer diameter size of foamblock 111 is precisely sized to the inside diameter size of outer shell114. Once the water tank is inverted and positioned onto the supportingfoam block 111, the remainder of the annular clearance space 115 isinjected with liquid foam insulation and the foaming process repeatsitself very similar to what is already been described with regard to theearlier embodiments. Similarly to the earlier embodiments, any spaces orvoids left along the lower portion or bottom of the outer shell andwater tank will be filled with dry insulation such as fiberglass. Whenthe water heater construction is gas, additional fiberglass will berequired around the burner portion in view of the high temperatureswhich are generated.

With reference to FIG. 12, instead of simply a free foamed block 111, ashaped enclosure 116 is provided whose outer size and contour isvirtually identical to that of foam block 111.

There are a variety of options for enclosure 116 which will ultimatelybe filled with liquid foam or fiberglass insulation. If liquid foam isinjected into enclosure 116, it will be through a small opening in theouter skin of enclosure 116 and foaming in place to completely fill thisenclosure. As one alternative fiberglass insulation is used, it can bepacked into this enclosure either under a normal atmosphere or under anevacuated condition. As yet another alternative a vacuum can be drawn onthe cavity within enclosure 116. When completed, enclosure 116 as filledwith insulation will receive the inverted top portion of the inner tankwith fitting 112 extending therefrom and into the clearance space whichis lined with the generally cylindrical gasket seal 113 similar to theillustration of FIG. 11. Another option for enclosure 116 is to increasethe wall thickness of the enclosure material and to construct thatenclosure of a generally flexible, fluid-impermeable material and allowthe flexible nature and the thickness of the wall to adjust orcompensate for minor tolerance variations and alignment. As thisenclosure fits within the outer shell and as the water tank rests ontop, there is a certain self-aligning and tightly sealed fit.

Referring to FIG. 13, a further manufacturing convenience for the waterheater construction according to the present invention is illustrated.In all of the foregoing embodiments, the inverted water tank and shellwere configured so as to simply be inverted without much reference as tothe nature of the fixture or support structure which would hold thisinverted shape and prevent any damage to the top portion of the waterheater where the flue and water inlet and water outlet fittings exit. Inthe illustration of FIG. 13, the inverted water heater 118 rests on topof a cardboard support panel consisting of at least two layers 119 and120. These cardboard layers will typically be part of an overallpackaging concept which additionally includes an oppositely disposedcardboard panel covering the base of the water heater with sufficientbanding and side support features to constitute a complete carton. As isillustrated, there is a pair of generally cylindrical clearance openings121 and 122 which receive the water inlet and water outlet fittings 123and 124. The water heater 118 includes an inner water tank 125, asurrounding outer shell 126 and a top cover 127. Top cover 127 restsdirectly against the top cardboard layer 119. As with earlierembodiments the shell and cover may be molded as an integral unitincluding virtually any of the seals and design concepts alreadydescribed herein. An additional opening is provided for the flue in theevent a gas water heater is inverted.

By utilizing the cardboard package as a support fixture for water heater118, it is envisioned that the package can be virtually completed andthen inverted at which point it receives the inverted water heater in anunfoamed condition. The water heater is then stabilized within thepackaging and the liquid foam insulation is injected into the annularspace so as to first fill the top clearance space directly above theinner water tank. This is the same foaming method as described for theearlier embodiments and the advantage of this particular construction isthat once the foaming is completed, the bottom cover can be added, theremainder of the packaging completed, and after the foam sets the entirewater heater assembly and packaging can then be returned to its normalupright condition and is ready for shipment.

Other acceptable arrangements for the FIG. 13 support structure forwater heater 118 are illustrated in FIGS. 13A-13C. In place of or inaddition to cardboard layers 119 and 120, foam insulation panels orforms may be used. Layers 119 and 120 may be fabricated out of foam ormay be a lamination of cardboard and foam in a wide variety of materialsand thicknesses. It is also envisioned for a surrounding ring or frameof foam or corregated cardboard to be used as a means of side supportsurrounding the outer shell.

In FIG. 13A, the individual foam or corrugated cardboard layers128a-128d are disposed above lower panels 119a and 120a. The size ofpanels 119a and 120a is greater than their counterparts in FIG. 13 so asto extend beyond the sides of the outer shell 126 and provide an outerlip or surface for layers 128a-128d to rest upon. The number, thicknessand material of layers 128a-128d may be varied depending upon desiredmaterial strengths and the overall height of the surrounding wall formedby the lamination or stack of layers.

Regardless of whether panels 119a and 120a are generally circular,square or rectangular, layers 128a-128d will have a matching outerperipheral shape. The inner edge of these layers is sized and shaped soas to provide a close fit (without interference) with the outer shell126. This close fit in combination with the openings for the outletfittings provides a means to align concentrically the tank and shellprior to foaming assuming that the opening locations are properly placedrelative to the inner edge of the layers 128.

Referring to FIG. 13B the entirety of the panels and layers of FIG. 13Ais replaced with a molded foam block 129 of material in final form withtwo openings for the plumbing outlet fittings and an outer wall toretain the shell and help maintain shell and tank concentricity. Foamblock 129 may be fabricated in its entirety out of polystyrene orsimilar rigid foam or could be molded as an integral unit out of othersynthetic materials or plastics.

Referring to FIG. 13C, an alternative construction for the block ofmaterial of FIG. 13B is illustrated. Block 129a includes a vacuum-formedshape comprising an outer skin or envelope 129b which is filled withsupport material 129c. The filler material is selected based upon needsfor rigidity and support and may be loose filled or packed.

Referring to FIG. 14, a further variation to the foregoing embodimentsis illustrated and it is to be understood that these changes are able tobe incorporated into all of the foregoing embodiments even though thespecific features are only illustrated as to an electric water heater.More particular, the water heater 130 of FIG. 14 includes an inner watertank 131, a generally cylindrical outer shell 132 and a top cover 133.The inner water tank and outer shell define a generally cylindricalannular clearance space 134 therebetween. Water inlet and water outletfittings 135 and 136, respectively, exit from the top of the inner watertank through openings in the top cover 133. In view of the fact thatthere is a desire to make the finished configuration as uniform andappealing in aesthetics as possible, it is desirable to have a generallyuniform and cylindrical shape to the outer shell. In order to assist inthis manner and to maintain a uniform foam thickness within the annularclearance space, and to prevent any shifting of the outer shell relativeto the water tank, such as from side to side which would increase theannular clearance space on one side and reduce it on the opposite side,a plurality of side and top spacers are provided. Side spacers 137extend between the outer surface of the inner tank and the inner surfaceof the outer shell. Top spacers 138 extend between the top surface ofthe inner tank and the inner surface of the top cover.

Referring to FIG. 15, a further variation of a water heater constructionaccording to the present invention is provided. As an alternative to thefixturing for the present invention and in order to provide a supportsurface for the inverted water tank and shell and as a means to preventthe leakage of any liquid foam into the threaded interior of theplumbing fittings, water heater 140 includes a pair of threaded plugs141 and 142 which extend through top cover 143 into plumbing fittings144 and 145. Plugs 141 and 142 are threadedly received by fittings 144and 145, respectively. As a consequence, the enlarged heads of thesethreaded plugs provide a support surface for the inverted water heater140 and with a tight threaded fit prevent any liquid from leaking in andaround these plumbing fittings.

While the invention has been illustrated and described in detail in thedrawings and foregoing description, the same is to be considered asillustrative and not restrictive in character, it being understood thatonly the preferred embodiment has been shown and described and that allchanges and modifications that come within the spirit of the inventionare desired to be protected.

What is claimed is:
 1. A water heater construction comprising:an innerwater tank; outer enclosure means disposed over and around said innerwater tank and defining therebetween a clearance space; thermalinsulation material foamed in place between the tank and outer enclosuremeans in said clearance space; and said foamed insulation materialhaving greater uniformity in cell structure in the volume disposed overthe top of said inner water tank than in the lower portion of the volumeof said foamed insulation material disposed around the side of saidinner water tank.
 2. The water heater construction of claim 1 whereinsaid enclosing means includes a generally cylindrical outer shell and agenerally cylindrical cover joined thereto.
 3. The water heaterconstruction of claim 2 wherein said inner water tank includes aplurality of plumbing fittings extending from said tank and through saidenclosing means and wherein said water heater construction furtherincludes gaskets sealing the interface between said fittings and saidenclosing means.
 4. The water heater construction of claim 1 wherein anyportion of said clearance space below said foamed insulation material isfilled with another type of insulation material different from saidfoamed insulation material.
 5. The water heater construction of claim 1wherein a plurality of spacers are disposed between the outer surface ofsaid inner tank and the inner surface of said enclosure means so as tomaintain a desired spacing therebetween.
 6. The water heaterconstruction of claim 1 wherein any portion of said clearance spacebelow said foamed insulation material is filled with another volume offoamed insulation obtained from a separate foaming operation.
 7. Thewater heater construction of claim 1 wherein said inner tank includes aplurality of plumbing fittings and said outer enclosure means includesclearance openings for said fittings, the location of said openingsproviding control of the position of said water tank within said outerenclosure means.
 8. A water heater construction comprising:an innerwater tank; outer enclosure means disposed over and around said innerwater tank and defining therebetween a clearance space; thermalinsulation material foamed in place between the tank and outer enclosuremeans in said clearance space; and said foamed insulation materialhaving greater uniformity in foam density in the volume disposed overthe top of said inner water tank than in the lower portion of the volumeof said foamed insulation material disposed around the side of saidinner water tank.
 9. The water heater construction of claim 8 whereinsaid enclosing means includes a generally cylindrical outer shell and agenerally cylindrical cover joined thereto.
 10. The water heaterconstruction of claim 9 wherein said inner water tank includes aplurality of plumbing fittings extending from said tank and through saidenclosing means and wherein said water heater construction furtherincludes gaskets sealing the interface between said fittings and saidenclosing means.
 11. The water heater construction of claim 8 whereinany portion of said clearance space below said foamed insulationmaterial is filled with another type of insulation material differentfrom said foamed insulation material.
 12. The water heater constructionof claim 8 wherein a plurality of spacers are disposed between the outersurface of said inner tank and the inner surface of said enclosure meansso as to maintain a desired spacing therebetween.
 13. The water heaterconstruction of claim 8 wherein any portion of said clearance spacebelow said foamed insulation material is filled with another volume offoamed insulation obtained from a separate foaming operation.
 14. Thewater heater construction of claim 8 wherein said inner tank includes aplurality of plumbing fittings and said outer enclosure means includesclearance openings for said fittings, the location of said openingsproviding control of the position of said water tank within said outerenclosure means.
 15. A water heater construction comprising:an innerwater tank; outer enclosure means disposed over and around said innerwater tank and defining therebetween a clearance space; thermalinsulation material foamed in place between the tank and outer enclosuremeans in said clearance space; and said foam insulation material havinga greater foam density in the volume disposed over the top of said innerwater tank than in the lower portion of the volume of said foamedinsulation material disposed around the side of said inner water tank.16. The water heater construction of claim 15 wherein said enclosingmeans includes a generally cylindrical outer shell and a generallycylindrical cover joined thereto.
 17. The water heater construction ofclaim 16 wherein said inner water tank includes a plurality of plumbingfittings extending from said tank and through said enclosing means andwherein said water heater construction further includes gaskets sealingthe interface between said fittings and said enclosing means.
 18. Thewater heat construction of claim 15 wherein any portion of saidclearance space below said foamed insulation material is filled withanother type of insulation material different from said foamedinsulation material.
 19. The water heater construction of claim 15wherein a plurality of spacers are disposed between the outer surface ofsaid inner tank and the inner surface of said enclosure means so as tomaintain a desired spacing therebetween.